English

Etymology 1

Old English borian, "to pierce". Confer Dutch
boren, German bohren, Old Norse bora. Cognate with Latin forare, "to bore", "to piece".
Sense of wearying may come from a figurative use such as "to bore
the ears"; confer German drillen.

The caliber of a
gun; as a measurement it is generally used to refer to smoothbore guns such as
shotguns and muskets and is generally used as
equivalent to gauge
which is the number of balls per pound of lead, later expressed in
inches or millimeters; this use is generally archaic, though still
used in British English and the sport of paintball where smoothbore
barrels are standard. The exception is the .410 bore,
which is .410 inches.